Get on the phone and start hounding product reps.  They'll bend over backwards to get their product spec'd in your project.

call Ando

Suggestions below assume the 'exposed finish ceiling' is the underside of a concrete deck that needs to look 'finished' and clean:

If you are in the US, look up ACI standards for the condition. If you aren't in the US, it's still a good resource but the verbiage might be different. Other countries may have similar standards documents, not sure.

Don't use metal reinforcing chairs - they rust, leaving your ceiling iron-spotted. Unless you want that sort of thing or don't care.

The mix should be generated by structural concerns more than aesthetic, so talk to a structural engineer. Modify from that starting point when possible.

Seal joints in formwork and any space between conduit or other cast-in MEP items with waterproofing tape to prevent moisture transmission. Too much moisture moving through the form will cause discoloration and physical weakness where the moisture is leaving.

Melamine-faced plywood form panels work well for a smooth as-cast finish.

Plan locations of contraction joints in the drawings. Don't leave this up to the contractor.

^ When in doubt, call Ando. Or call Scogin/Elam. Or Allied Works. Lots of good examples out there depending on the appearance you are looking for. Hope this helps - good luck.